Universal Calibrator Unical 28531
The UniCal 28531 is portable, battery operated, precision instrument capable of sourcing as well as measuring mV/V/mA/ohm signals. It is designed to calibrate a broad spectrum of instruments from moving coil meters to process control systems and retain its precision over long periods in wide environmental conditions. It is also capable of acting as a current regulator or of powering Two-wire Transmitters while measuring their output. It offers optional 3½ or 4½ digit LCD display for cost-effective calibration. A self-check facility monitors its performance to assure dependability.
The 28531 is designed with field-proven circuit blocks using low-power integrated circuits. It operates on 7 AA size dry-cells or 7 AA size rechargeable Ni-Cd cells or an external Battery Eliminator. The battery voltage is monitored to provide low battery indication. A current limited DC/DC converter provides operating power to the circuitry for operational safety in hazardous locations. An exceptionally stable voltage/current source provides continuously variable precision mV/V/mA/O output signals with two ten-turn potentiometers. The 28531 is capable of powering Two-wire transmitters while measuring the transmitter current and can also be used as a transmitter simulator in two-wire loops. It can be also be used as a constant voltage/current regulator using external unregulated power supplies. The measuring circuit takes into account all possible error sources to ensure error-free measurement of the sourced or measured signal. A precision 3½ or 4½ digit A/D converter with an aged reference provides a stable display with excellent repeatability.
The Model 28531 is a general purpose calibrator which can be used either in the laboratory or taken around the plant for in-situ calibration of instruments and loops. It covers most of the process control instruments and is especially suitable for Commissioning and Maintenance.
OUTPUT SPECIFICATIONS
The 28531 sources or measures mV/V/mA/ohm signals, can simulates
or power 2-wire transmitters operating on 24V DC supplies.
Output Options
A choice of several ranges to meet most common requirements
| I/O Code |
Function & Range Switches |
Resolution |
| A (3½) |
20 mA |
200 Ω |
20 mV |
200mV |
N/Z |
1 in 2,000 |
| C (3½) |
20 mA |
200 Ω |
20 mV |
2V |
X1/X10 |
1 in 2,000 |
| D (4½) |
20 mA |
2000 Ω |
200 mV |
20V |
|
1 in 20,000 |
| E (4½) |
20 mA |
200 Ω |
200 mV |
20V |
|
1 in 20,000 |
| G |
User Specified within Output Limits |
Notes:
1. Bold Numbers indicate interlocked Switches
2. N/Z: N-Normal and Z-Zero Suppression
3. X1/X10: X1-Multiplied by 1 and X10-Multiplied by 10 |
Output Impedance
| Voltage |
: |
< 0.05 ohm |
| Current |
: |
> 1 Megohm |
Source Capacity (@ 90% Bat Voltage)
| Voltage |
: |
Upto 15V into 600 Ω or 20V into 800 Ω |
| Current |
: |
Upto 25 mA into 600 Ω or 20 mA into 800 Ω |
| Ohms |
: |
Upto the maximum specified range |
INPUT SPECIFICATIONS
Input Impedance
| Voltage |
: |
> 1 Megohm |
| Current |
: |
1 or 10 ohm depending on range |
| Resistance |
: |
Bridge Current of 0.1/1 mA depending on range |
Input Protection
Input/Output Terminals Protected for 24 V DC in Voltage & Ohms
Ranges, and upto double the range in mA Ranges
INDICATOR SPECIFICATIONS
Indicator Type
Indicators with the following resolutions to suit the selected
Range
| 3½ digit |
: |
12 mm LCD with a resolution of 1 in 2,000 |
| 4½ digit |
: |
8 mm LCD with a resolution of 1 in 20,000 |
INSTRUMENT ACCURACY
Accuracy at operating temperature between 22-32 °C,
valid within a one year Calibration Cycle
| 3½ digit |
: |
± 0.05% of rdg ± 0.02% of f.s. ± 1 dgt |
| 4½ digit |
: |
± 0.02% of rdg ± 0.01% of f.s. ± 2 dgt |
| Self-Check |
: |
Displays 1777±1 for 3½ and 17777±2 for 4½ dgt indicator |
POWER SUPPLY SPECIFICATIONS
Power Supply Options
| Option
A |
: |
7 Nos of AA size dry cells giving 10.5V |
| Option B |
: |
7 Nos of Ni-Cd Rechargeable AA cells giving 8.4V |
Battery Life
| Dry Cells |
: |
5 to 6 Hrs in continuous use at 12 mA output |
| Ni-Cd Cells |
: |
4 - 6 Hrs in continuous use at 12 mA output |
Low Battery
Indicated by lighting all decimals or "LO BAT" indicator
Mains Operation
A Jack is provided for operation on an external Battery
Eliminator
ENVIRONMENTAL SPECIFICATIONS
| Rated Temp |
: |
5 to 55°C |
| Humidity |
: |
Less than 90% RH ( Non-Condensing ) |
| Zero Drift |
: |
Less than 1dgt for every 10°C beyond the specified
ambient of 22 - 32°C |
| Span Drift |
: |
Less than 0.0015% of rdg / °C |
| Storage Temp |
: |
0 to 70°C (Without Batteries) |
MECHANICAL SPECIFICATIONS
| Enclosure
Size |
: |
125(W) x 200(H) x 55(D) mm |
| Enclosure Finish |
: |
Powder coated |
| Enclosure Weight |
: |
1.0 Kg (Without Batteries & Accessories) |
STANDARD ACCESSORIES
Battery Eliminator, Probe Set, Leather Case, Wooden Case,
Instruction Manual, Warranty Certificate, Calibration Certificate
Traceable to NPL.
Charger for Ni-Cd Cells if Power Supply
Option B is selected.
ORDERING INFORMATION
While ordering please specify the various options as per
the following ordering code
| Model No. |
I/O Option |
P.S. Option |
| 28531 |
X |
X |
Example
Specify 28531AA to order the Universal Calibrator with 3½ digit
12mm LCD display and ranges of 20 mA, 200ohms, 20mV,
200mV operating on 7 Nos of AA size dry cells. |
